Composition for enhanced bioremediation of oil

ABSTRACT

A particulate material, as well as a method of manufacturing and using the material, for promoting growth of petroleum degrading bacteria to aid in bioremediation of oil spills on water and in wetlands which consists of a core of microbial available nutrients having a coating, comprised of oleic acid and either stearic acid, palmitic acid, or a mixture thereof, which is lipophilic, and biodegradable, for retaining the nutrient in the oil for gradual release to microorganisms between applications of the material.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 08/051,626, filed Apr. 22, 1993, U.S. Pat. No.5,443,845.

FIELD OF THE INVENTION

This invention relates to a composition, and methods of using thecomposition, comprising a water soluble nutrient formulation including asource of molecular oxygen that is encapsulated in an oleophilic coatingmixture which provides a slow biologically mediated release of nutrientsto microorganisms which degrade oil. The invention further relates to amethod of manufacturing the material and a method of using the materialto achieve bioremediation of spilled oil.

BACKGROUND

Oil spills have occurred with increasing frequency as the growing demandfor petroleum products has been met by increased shipments of oil inocean going tankers, barge traffic and the like. Oil spills caused bynavigational errors, especially in the presence of rough weather andother factors, can cause devastating damage to the environment.

Much of the effort to cleanup such spills has centered on mechanicalmethods to contain and remove the spilled oil and to clean oilcontaminated areas. However, these methods are not entirely satisfactorybecause much of the oil either cannot be contained or escapescontainment. Even when contained, mechanical removal is at best onlypartial. In all oil spills, small amounts to the vast majority of thespilled oil remains in the affected areas after all best efforts toclean and remove the oil are completed.

It has long been known that oil is continuously being released into theenvironment by natural petroleum seeps. The quantity of oil released bythese natural seeps world wide annually exceeds the sum total of allworldwide petroleum hydrocarbon releases from all other sources (i.e.,oil spills, tanker washings, run-off, etc.). It is also well known thatthese large natural releases of petroleum do not accumulate in theenvironment nor cause damage to the world's ecosystem. The reasons forthis is that within the earth's ecosystem there is a well established,highly diverse and ubiquitously distributed population of microorganismsthat degrade petroleum hydrocarbons. The application of this knowledgeto utilize petroleum degrading microorganisms to treat spilled oil isknown collectively as the process or method of bioremediation.

The success or effectiveness of bioremediation is dependent upon keyfactors being simultaneously present. First, the presence of hydrocarbondegrading microorganisms, either naturally or by addition. Second, theremust be oxygen and water available to permit the microorganisms to bemetabolically active. Third, there must also be available sufficientquantities of biologically utilizable nitrogen and phosphorous to enablethe microbial population to rapidly metabolize the available petroleumhydrocarbons.

Microorganisms capable of degrading petroleum hydrocarbons can be foundin almost all natural bodies of water. The exact type of microorganismspresent in a given area of a spill may vary greatly yet each has theability to degrade oil. The elemental nutrient requirements of petroleumdegrading microbes are approximately the same as the microbes' averageelemental composition. The carbon, which makes up 48 percent of themicrobes composition, is obtained from the petroleum oil slick--lightsto crude in weight; C₇ to C₈₀ tars. However, the remaining elementalmaterials necessary to grow must be provided from either the surroundingwater or a supplementary source. If the supply of these other nutrients,especially nitrogen, phosphorous, sulfur, magnesium, potassium, calciumand sodium, are exhausted, then the microbe population will not grow anyfurther. When significant quantities of petroleum have been spilled in abody of water, essential nutrients must be applied to the petroleum tosustain microbial growth.

It is usually insufficient quantities of microbially available nitrogenand phosphorous that limit the rate of natural biodegradation of spilledoil in the environment. However, the application of water solublenitrogen and phosphorous to spills in aquatic environments has proven tobe ineffective because the nutrients are rapidly dissipated into thesurrounding water volume. Nutrient additive formulations have typicallysuffered from a number of problems including incomplete partitioning ofthe nutrients into the oil phase, poor biodegradability of encapsulatingmaterials and the difficulty and high cost of manufacturing.

In U.S. Pat. No. 3,883,397, Townsky discloses a particulate materialmade of a nutrient formulation coated with a lipophilic material whichsuspends the material in the oil or near the oil-water interface. Thiscoating is composed of magnesium, aluminum and calcium salts oflipophilic fatty acids, specifically magnesium stearate.

It would be desirable to have a composition that would retain essentialmicrobial available nutrients, such as nitrogen, phosphorous and iron,within the oil phase of an oil and water mixture as occurs in an oilspill in an aquatic or wetland environment. It would also be desirablefor the nutrient formulation to be able to sustain growth ofmicroorganisms throughout the body of oil. Also it would be desirablefor the nutrient formulation to be supplemented with oxygen releasingcompounds to provide molecular oxygen within the oil matrix to enhancegrowth of aerobic microorganisms. It would further be desirable if thenutrients and oxygen releasing compounds were released and/or activatedat a slow and controlled rate based upon biological demands of themicroorganisms through degradation of the encapsulating coating andpartial dissolution of the coating into the oil phase.

SUMMARY OF THE INVENTION

The present invention provides a particulate material for promotinggrowth of petroleum degrading bacteria. Each particle of the nutrientmaterial comprises a core of water soluble microbial available nutrientsselected from the group consisting of nitrogen in the form of ammoniumor urea compounds, phosphorous in the form of microbial availablephosphate compounds, iron in the form of microbial available ironcompounds, and oxygen in the form of various hydrogen peroxidecompounds. The coating formulation of this invention uses a mixture ofsaturated and unsaturated fatty acids to form a coating material whichis readily biodegradable, has physical properties making it efficientfor encapsulating microbial nutrients, increases the oil phasepartitioning of the composite and reduces the cost of manufacture.

More particularly, the encapsulation for the core of nutrients is formedof an oleophilic and biodegradable coating comprising oleic acid and acarboxylic acid selected from the group consisting of stearic acid,palmitic add, and mixtures thereof. The preferred ratio of oleic acid tothe selected carboxylic acid is between about 70:30 and about 30:70 byweight.

The invention also provides a process of manufacturing the coatednutrient material, which comprises mixing microbial nutrients togetheras dry ingredients and grinding them into a powder sufficient to passthrough. a number 40 sieve. A coating mixture is prepared fromcommercial grade stearic acid and oleic acid at a preferred ratio of40:60 by weight. The coating mixture is melted by heating to 100° C. andresolidified to form a homogeneous composite, remelted at 100° C. Uponcooling to 65° C., the coating is blended into the nutrients at a ratioof 90% nutrients to 10% coating by weight.

The invention further provides a method of using or applying coatednutrients to foster microbial growth for conversion of an oil slick. Thematerial is applied to an oil spill as soon as possible to beginmicrobial development. The preferred dosage is a rate of 10 to 15 poundsper barrel of spilled oil. The material can be reapplied at timeintervals ranging from 48 to 96 hours. The application can be achievedby any conventional means including, but not limited to, spraying,dusting, and dropping from an airplane.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereofwhich are illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a flow diagram of the method of manufacturing the presentcomposite material; and

FIG. 2 is a sectional view through a reaction chamber where thecomposite material may be manufactured.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a particulate composition having anutrient formulation, an oxygen releasing compound, and an oleophiliccoating. The preferred nutrient formulations for fostering the growth ofpetroleum degrading bacteria have the following exemplary proportions:

between about 90 and about 94 percent (%) by weight ammonium sulfate(NH₄)₂ SO₄ !, urea or combinations thereof as a source of nitrogen;

between about 5 and about 8 percent (%) by weight potassium phosphatedibasic K₂ HPO₄ ! or substitutions such as potassium phosphate monobasicKH₂ PO₄ ! or calcium phosphate monobasic CaHPO₄ !, dibasic Ca(H₂ PO₄)₂ !or tribasic Ca₃ (PO₄)₂ !, urea phosphate, or ammonium phosphate NH₄ H₂PO₄ !; and

between about 1 and about 2 percent (%) by weight ferrous sulfate FeSO₄! or a substitution such as ferrous surfate heptahydrate FeSO₄ *7H₂ O!.

The most preferred nutrient formulations have an ammonium/urea:phosphatecompound:iron compound ratio between about 90:8:2 and about 94:5:1. Theprecise formulation of nutrients can vary according to the specific typeof microorganism present in the water, the composition of the spilledoil and the current costs of each nutrient source. The nutrientformulation is mixed together as dry ingredients and ground into apowder sufficient to pass a U.S. standard number 40 sieve.

It is preferred that the nutrient formulation be mixed with compoundsthat provide a source of molecular oxygen including, but not limited to,urea hydrogen peroxide. These compounds release molecular oxygen (O₂) byenzymatic or chemical reactions. This molecular oxygen is utilized bythe microorganisms to enhance and promote aerobic metabolism throughoutthe oil rather than solely at the interface of the oil.

These oxygen releasing compounds may be incorporated into either thenutrient formulation or within and as part of the fatty acid coatingmatrix described below. It is preferred that the oxygen releasingcompounds comprise between about 1 and about 20 percent (%) by weight ofeither the nutrient formulation, the oleophilic coating, or bothtogether.

Because hydrogen peroxide is known to be unstable in aqueous solutionsand is also toxic to microorganisms at high concentrations, the oxygenreleasing compounds of hydrogen peroxide are incorporated asencapsulated particulates. Utilization of hydrogen peroxide and peroxidecompounds to enhance microbial growth has been well documented, but hasseen little practical application in the field because of the previouslynoted problems--stability and toxicity. The encapsulation of particulateperoxide compounds (as example being, but not limited to, urea hydrogenperoxide) stabilize the materials by keeping the compounds from rapidlyreacting with water or divalent cations which promote peroxidedegradation (for example Fe⁺²). The encapsulation also prevents thetoxicity of rapid peroxide decomposition from effecting themicroorganisms through regulated release of compounds at concentrationsthat support microbial growth and limit promotion of toxic oxygenradicals.

In order to prevent rapid dilution of these water soluble nutrients uponapplication, a water insoluble coating is applied which is lipophilicand oleophilic. This coating is vital to the retention of the nutrientproduct in the oil phase where it is needed to support bacterial growth.It is also important that the coating release the nutrients and oxygengradually over the period between applications.

The rate at which the product components are released is determined bypartial dissolution of the coating in the oil phase and biologicaldegradation of the coating caused by the microorganisms. As hydrocarbondegrading microbes utilize the available petroleum hydrocarbons, theyconcomitantly metabolize the component fatty acids constituting thecoating mixture which encapsulate the essential nutrient formulation. Asthe coating becomes perforated, the inner core of water solublenutrients and oxygen releasing components are dissolved into the oil. Inthis fashion, the encapsulated nutrients are made available over timeupon biologically mediated demand. Supplemental applications of thenutrient composite can be made to ensure sufficient nutrientconcentrations are available to foster and sustain enhanced microbialgrowth.

The coating formulation of this invention uses a mixture of saturatedand unsaturated fatty acids to form a coating material which is readilybiodegradable, has physical properties making it efficient forencapsulating microbial nutrients, increases the oil phase partitioningof the composite and reduces the cost of manufacture. More particularly,the encapsulation for the core of nutrients is formed of an oleophilicand biodegradable coating comprising oleic acid and a carboxylic acidselected from the group consisting of stearic acid, palmitic acid, andmixtures thereof. The preferred ratio of oleic acid (unsaturated) to theselected carboxylic acid (saturated) is between about 70:30 and about30:70 by weight.

The coating of the present invention may be prepared with any ratio ofsaturated fatty acids and unsaturated fatty acids where the coating issufficiently biodegradable to release nutrients as needed and has asufficiently high melting temperature to allow the coated nutrient to bestored without clumping together. The preferred coating formulationcomprises the following:

between about 30 and about 70 percent (%) by weight saturated fattyacids, such as stearic acid CH₃ (CH₂)₁₆ COOH!, including commercialpreparations such as EMERSOL 132, PROMULSIN and PROVISCOL WAX, orpalmitic acid CH₃ (CH₂)₁₄ COOH!, or mixtures thereof; and

between about 30 and about 70 percent (%) by weight oleic acid CH₃(CH₂)₇ CH--CH(CH₂)₇ COOH!.

It is most preferred that the coating include between about 2% and about5% of stearamide CH₃ (CH₂)₁₆ CONH₂ !, palmitamide CH₃ (CH₂)₁₄ CONH₂ ! oroleamide CH₃ (CH₂)₇ CH:CH(CH₂)₇ CONH₂ ! to extend the period of timeover which the nutrients are released and to additionally enhance thenutrient availability of the coating mix itself.

To prepare the coating formulation, the fatty acids are mixed together,heated to melting at 100° C., then cooled to produce a homogenous solidcomposite mixture. Before being applied to the nutrients, the coatingmixture is remelted at 100° C. to achieve a smooth flowing liquid. Thenthe coating is cooled to about 65° so that it will solidify quickly whenapplied to the nutrients.

Using the coating formulation just described, an encapsulatedparticulate composite can be manufactured in at least two ways. Using aconventional manufacturing method, the coating material is added as aliquid into the dry solids mixer while the nutrients are being blended.An appropriate dry solids mixer for this method is a Ross ribbon blendermade by Ross Manufacturing. It may become necessary to equip the ribbonblender with a chopper attachment to reduce clumps that form in themixing process. The coating formula is added to the nutrients at a ratiobetween about 8 and about 20 percent (%) by weight to ensure adequateencapsulation, while the preferred ratio is about 10% by weight. Thecoated nutrient mixture must be removed from the mixer and screened toremove clumped material, preferably by passing the coated nutrientthrough a U.S. standard number 20 sieve. The sifted material is thenremixed with between about 1 and about 1.5 percent (%) amorphous silicaor any other standard anti-caking agent to maintain the free flowingproperties of the invention.

Now referring to FIG. 1, a second method of manufacturing the compositeis detailed. Mixed and powdered nutrients are sprayed as an aerosol intoa vessel. The encapsulation coating is also aerosolized and sprayed as amicro-droplet sized mist into the vessel where is contacts the powderednutrients and solidifies thereon. An apparatus for carrying out thismethod of manufacture is illustrated in FIG. 2. The advantages of thisnovel method of manufacture include reduced clump formation and areduction in the time and cost of screening the composite through asieve. Furthermore, the equipment can be designed as a continuous flowmachine, with raw ingredients entering at one end of the machine andessentially finished product exiting at the other. An anti-caking agent,such as amorphous silica, may be added to the coated product to maintainproduct flow properties.

A description of how the coating apparatus functions is given hereafter.The reaction chamber 10 is a vertical vessel in which the compositematerial is made. Gas flow nozzles 12 and 14 provide a steady flow ofwarm air to the mixing zone 16. The warm air helps regulate thetemperature of the mixing zone 16 to achieve proper coating of thenutrients and also determined the retention time of the powderednutrients in the mixing zone. Powdered nutrients are sprayed throughnozzle 18 into mixing zone 16 as a suspended aerosol. The nutrientaerosol is then contacted with hot liquified encapsulation coatingsprayed through nozzle 20 into the mixing zone 16 to form a fully orpartially encapsulated composite.

The composite material can be manufactured either as a powder, pellet orparticulate. To manufacture a powdered composite, a gas or air flow isdirected downward from nozzle 12 such that the nutrients remain in themixing zone 16 for only a short period of time. In order to manufacturea pelletized composite material, the gas or air flow is directed upwardfrom nozzle 14 to mixing zone 16 and out through air pressure reliefvalves 17 and 19 at the top of reaction chamber 10. This upward flow ofgas provides an uplifting force or air cushion which maintains thenutrients in the mixing zone 16 until sufficiently coated to agglomerateand increase in weight. Once the pellet reaches a given weight,gravitational forces will become greater than the upward gas lift andthe pellet will begin to fall.

As the composite material falls out of the chamber 10, it passes througha cooling zone 22. The zone 22 is cooled by forcing chilled gas or airthrough nozzle 24 and downward through distributor 26. When thecomposite material comes into contact with the chilled gas, the coatingis solidified.

The finished composite then passes through a conical restriction 28 to acollection mechanism 30, typically a dust collector, where the compositeis collected and ready for use. Air pressure is relieved throughconnector pipe 32 to bag filter 34.

In an alternative method of manufacturing the composite, theencapsulation coating may be brought into contact with the nutrientaerosol by dissolving the encapsulation formulation in a rapidlyevaporating solvent. In this manner, the dissolved coating mixtureprecipitates onto the surface of the base powder.

The composite product can be applied to a oil spill using conventionalpowder spraying equipment with no pre-mixing or dilution required.Application of the product may also be achieved by hand broadcasting,dust blowing or by aircraft. Soft clumps may form after prolongedstorage, but they are easily broken by mechanical mixing.

Initial applications to open water spills should be 5-15 pounds ofproduct per barrel of spilled oil (approximately 14-43 kilograms percubic meter of spilled oil), but should not exceed 250 pounds per acre(280 kilograms per hectare) of surface area per application. The productshould be applied to spilled oil as soon as possible following spillageto stimulate natural oil utilizing microbial populations to maximizebiodegradation activity. Follow-up applications may be made at 48-96hour intervals until the oil is completely consumed. The exact intervaland the weight of product per acre is based upon factors such as thedegree of reduction in oil by clean-up activities and natural loss byevaporation, droplet formation, dispersion, composition of the oil, typeof bacteria present and microbial activity. Application of this novelproduct to spilled oil does not significantly alter the physicalconsistency of the spilled oil, and will not adversely impactconventional clean-up activities, nor will conventional containment andremoval activities adversely harm the activity of the coated nutrientproduct.

Application of the product to wetland spills should be limited to thearea of oil contamination. The best possible estimate of quantity of oilconcentration is used to calculate the quantity of product to be appliedin this instance. Recommended application is 10-25 pound of product perbarrel of oil spilled (approximately 28-71 kilograms per cubic meter ofoil spilled), but should not exceed 250 pounds per acre (280 kilogramsper hectare). The product should be directly applied to the oilcontaminated habitat by use of dust delivery equipment. The productshould be applied directly to any visible oil and all visible oil shouldbe lightly coated. In general, successive light treatments is preferredover a single heavy application. Follow-up application should be made atweekly or bi-weekly intervals. The product is most effective where oilhas not formed a hard exterior crust that prevents the nutrient productfrom integrating into the oil layer itself.

Application of the product to beach spills should be made directly ontothe oil at 15-30 pounds per barrel of spilled oil (approximately 43-86kilograms per cubic meter of oil spilled). Where the spilled oil ismixed with sand or beach cobbles, the product should be directly sprayedonto contaminated areas and mixed into the beach material if possible.In this situation, an application may be increased to 300 pounds peracre (approximately 336 kilograms per hectare).

It is important that the nutrient materials have low toxicity since theyare often applied in areas that contain fish and other wildlife. Inorder to avoid most toxicity problems, the amount of nutrient materialapplied is never to exceed 300 pounds per acre (approximately 336kilograms per hectare).

To confirm the effectiveness and the non-toxic nature of the material,the following laboratory tests were carried out.

EXAMPLE 1

Biodegradation potential was assessed by treatment of artificiallyweathered crude oil treated with a oleophilic nutrient mixture withoutan oxygen releasing compound. An identical untreated control wasmaintained for comparison.

The analysis was conducted in a dual chambered continuous flowingreaction chamber using filtered natural seawater from Galveston bay(collected at Texas A&M University, Pelican Island Marine Station.)Seawater was continuously exchanged during the experiment at 40milliliters per minute with no recycling. The seawater was maintained at33 ppt salinity and 29° C. to approximate summer conditions in GalvestonBay. 25 milliliters of oil was added to the chamber to obtain a surfaceoil thickness of 1.225 millimeters, which is equivalent to 30.6 barrelsof oil per acre (approximately 12 cubic meters of oil per hectare),assuming uniform spreading of oil. The oil was prepared from AlaskanPrudhoe Bay crude, sparged with air for 4 hours prior to application towater, and allowed to spread on the water for 12 hours prior totreatment.

The oil was then treated with 0.30 grams of a nutrient mixture composedof 0.256 grams of (NH₄)₂ SO₄, 0.011 grams of KH₂ PO₄, and 0.003 grams ofFeSO₄ *7H₂ O, coated with a mixture of 0.018 grams oleic acid and 0.012grams stearic acid. The reaction vessel was continuously aerated withbubblers at a rate of 250 milliliters of air per minute. After 48 hours,a follow-up application was made using only one-half the amount ofnutrient mixture as in the original application.

The quantity of surface oil present is measured by adherence of thesurface oil to glass fiber disks (0.633 cm² per disk, total 5 disks persample). Adherent oil is then extracted from the disks with GC grademethylene chloride (Burdick and Jackson, obtained from BasterScientific, Inc.) The samples were analyzed by M.B.A. Labs, Houston Tex.using gas chromatography with flame ionization detection. Analysis waslimited to hydrocarbons of weight C₁₅ or greater and gravimetricquantitation for total petroleum hydrocarbons.

                  TABLE I                                                         ______________________________________                                        This table contains the results of a comparison of total                      hydrocarbons from surface oil (mg/cm.sup.2 of film area) between a            control                                                                       and a sample with the nutrient mixture added. . .                             TIME (HOURS) CONTROL   NUTRIENT MIXTURE                                       ______________________________________                                        0            20.6      18.4                                                   26           13.6      6.5 (53.5%)                                            32           14.8      6.0 (45.4%)                                            48           10.5      2.8 (29.9%)                                            72           4.1       1.6 (43.7%)                                            240          5.1       2.3 (50.5%)                                            ______________________________________                                    

The figures in parenthesis represent the percent difference in reductionof oil between the treated and untreated oil as measure after each timeperiod.

EXAMPLE 2

A nutrient mixture and coating were prepared as described in example 1.The toxicity of the product as expressed by reduced survival oforganisms exposed to various dilutions of the product was determinedthrough a 48 hour acute static renewal bioassay using Mysidopsis bahiaand Cyprinodon variegatus. E.P.A./600/4-85/013 test protocol wasfollowed. All organisms were maintained at room temperature with alight/dark cycle of 16/8. Dilution water was made from Tropic MarineSynthetic Sea Salt and was aerated for 24 hours before use in the test.The test was performed in 600 ml polypropylene diSPo beakers rinsed inthe dilution water. Ten organisms of Mysidopsis bahia were placed in 200ml of dilution water making a 5 cm depth. Ten organisms of Cyprinodonvariegatus were placed in 500 ml of dilution water making a 9.5 cmdepth.

Dissolved oxygen, pH, conductivity and salinity, alkalinity and hardnesswere measured before water renewal. CdCl supplied by the E.P.A. was usedas the reference toxicant for both of the Mysidopsis and Cyprinodonorganisms. Both the Mysidopsis and the Cyprinodons used in this testwere obtained from Aquatox, Inc., and were approximately 27 days old atthe time of testing. Both batches of organisms were acclimated to theproper salinity, by adding 300 ml of synthetic, fresh water, every houruntil test initiation. The salinity was 11 parts per thousand for bothbatches of organisms before use in the test. Holding water and sampletemperatures were 24° C. at test initiation. The test ran 23 hoursbefore starting water renewal. The test finished 1 hour later.

The E.P.A. Probit Analysis Program for Calculating Values, Version 1.4provided the following results:

    ______________________________________                                        Mysidopsis bahia EC.sub.50  = 0.12 g/l                                                              (>300 pounds/acre)                                      CdCl EC.sub.50  = 118.5 ug/l                                                  Cyprinodon variegatus EC.sub.50  = 0.50 g/l                                                         (>1300 pounds/acre)                                     CdCl EC.sub.50  = 7823.7 ug/l                                                 ______________________________________                                    

The test illustrates that the coated nutrient mixture is only slightlytoxic and can be used safely in quantities up to 300 pounds/acre.

It will be understood that certain combinations and subcombinations ofthe invention are of utility and may be employed without reference toother features in subcombinations. This is contemplated by and is withinthe scope of the present invention. As many possible embodiments may bemade of this invention without departing from the spirit and scopethereof, it is to be understood that all matters hereinabove set forthare to be interpreted as illustrative and not in a limiting sense.

While the foregoing is directed to the preferred embodiment, the scopethereof is determined by the claims which follow:

What is claimed is:
 1. A composite material for promoting growth ofhydrocarbon degrading microorganisms, comprising:a water soluble,microbial available nutrient formulation; an oxygen releasing compound;and a sacrificial oleophilic, lipophilic, partially oil soluble andbiodegradable coating.
 2. The composite material of claim 1 wherein theoxygen releasing compound is a peroxide compound.
 3. The compositematerial of claim 2 wherein the oxygen releasing compound is ureahydrogen peroxide, and wherein the composite material comprises betweenabout 1 and about 20 percent by weight of urea hydrogen peroxide.
 4. Thecomposite material of claim 1 wherein the coating comprises a saturatedfatty acid selected from the group consisting of stearic acid, palmiticacid, and mixtures thereof and an unsaturated fatty acid selected fromthe group consisting of oleic acid, linoleic acid and mixtures thereof,wherein said coating encapsulates said core.
 5. The composite materialof claim 1 wherein said nutrients include nitrogen in the form of anammonium compound, phosphorous in the form of a microbial availablephosphate compound, and iron in a form of microbial available ironcompound.
 6. The composite material of claim 4 wherein said coatingfurther comprises an amine substituted form of a fatty acid selectedfrom the group consisting of amine substituted forms of stearic acid,palmitic acid and oleic acid, and wherein the ratio ofsaturated:unsaturated:amine-substituted fatty acids is in the range ofabout 30:68:2 to about 65:30:5 by weight.
 7. The composite material ofclaim 1 wherein the coating comprises a saturated fatty acid selectedfrom the group consisting of stearic acid, palmitic acid, and mixturesthereof and an unsaturated fatty acid selected from the group consistingof oleic acid, linoleic acid and mixtures thereof, wherein said coatingencapsulates said core; andwherein said nutrients comprise nitrogen inthe form of an ammonium compound, phosphorous in the form of a microbialavailable phosphate compound, and iron in a form of microbial availableiron compound.
 8. The composite material of claim 7 wherein thecomposite material comprises between about 1 and about 20 percent byweight of the oxygen releasing compounds.
 9. The composite material ofclaim 8 wherein the oxygen releasing compound is a peroxide compoundselected from the group consisting of urea hydrogen peroxide, sodiumpercarbonate, calcium peroxide, potassium peroxide, magnesium peroxide,and mixtures thereof.